1²-2²+3²-4²+5²-6²...-100²+101²=____
2011-03-12
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1²-2²+3²-4²+5²-6²...-100²+101²
=(101²-100)²+(99²-98²)+...+(3²-2)²+1²
=101+100+99+...+2+1
=(101+1)*101/2
=5151
=(101²-100)²+(99²-98²)+...+(3²-2)²+1²
=101+100+99+...+2+1
=(101+1)*101/2
=5151
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12-22+32-42+52-62...-1002+1012=
=1+(3-2)(3+2)+(5-4)(5+4)+(7-6)(7+6)_...-(101-100)(101+100)
=1+2+3+4+5+...+101+100
=101(1+101)/2
=5151
=1+(3-2)(3+2)+(5-4)(5+4)+(7-6)(7+6)_...-(101-100)(101+100)
=1+2+3+4+5+...+101+100
=101(1+101)/2
=5151
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1²-2²+3²-4²+5²-6²...-100²+101²
=(1+2)(1-2)+(3+4)(3-4)....(99+100)(99-100)+101²
= 101² - (1+2+3....+100)
=101²-(1+100)100/2
=101(101-50)=(50+1)(100+1)=5000+150+1=5151
=(1+2)(1-2)+(3+4)(3-4)....(99+100)(99-100)+101²
= 101² - (1+2+3....+100)
=101²-(1+100)100/2
=101(101-50)=(50+1)(100+1)=5000+150+1=5151
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